a first housing having a first piston defining a first chamber and a second chamber, the first chamber to receive a control
fluid and the second chamber to receive a process fluid from a process system, the first chamber to be oriented above the
second chamber when the control fluid power apparatus is coupled to a control valve assembly; and

a second housing having a second piston defining a third chamber and a fourth chamber, the third chamber to receive the control
fluid and the second chamber is to receive the process fluid, the third chamber to be oriented above the fourth chamber when
the control fluid power apparatus is coupled to the control valve assembly.